Sum-frequency generation utilizing two cw single-mode Nd:YAG lasers an
d a congruent lithium niobate crystal yielded 3.4 mW of very narrow-ba
nd (10 kHz over 1 ms) tunable 589-nm cw radiation. This simple solid-s
tate light source is well suited for high-resolution spectroscopy of t
he sodium D-2 line, as was demonstrated with both conventional and FM-
modulated saturation spectroscopy. (C) 1997 Optical Society of America
.